Question

Assume that the node of a linked list is in the usual info-link form with the info of type int. The following data, as described in parts (a) to (d), is to be inserted into an initially linked list: \(72,43,8,12 .\) Suppose that head is a pointer of type nodeType. After the linked list is created, head should point to the first node of the list. Declare additional variables as you need them. Write the \(C++\) code to create the linked list. After the linked list is created, write a code to print the list. What is the output of your code? a. Insert 72 into an empty linked list. b. Insert 43 before 72 c. Insert 8 at the end of the list. d. Insert 12 after 43

Short answer

Output: 43 12 72 8

Step-by-step solution

Set up the Node Structure

First, we need to define the node structure. This structure will have two members: an integer called `info` to store the data and a pointer called `link` that points to the next node in the list. ```cpp struct Node { int info; Node *link; }; ```

Initialize the Head Pointer

The linked list begins with an empty state, so the head pointer should initially point to `nullptr`. ```cpp Node *head = nullptr; ```

Insert 72 into an Empty List

To insert 72, create a new node, set `info` to 72, `link` to `nullptr`, and make the head point to this new node. ```cpp Node *temp = new Node; temp->info = 72; temp->link = nullptr; head = temp; ```

Insert 43 Before 72

Create another node for 43. Set its `link` to the current head, and then update the head to point to this new node. ```cpp temp = new Node; temp->info = 43; temp->link = head; head = temp; ```

Insert 8 at the End of the List

Create a node for 8 and traverse the list from the head until the last node is found. Set this last node's `link` to point to the new node ```cpp temp = new Node; temp->info = 8; temp->link = nullptr; Node *current = head; while (current->link != nullptr) { current = current->link; } current->link = temp; ```

Insert 12 After 43

Find the node with `info` 43, create a new node for 12, and adjust the links accordingly. ```cpp temp = new Node; temp->info = 12; current = head; while (current != nullptr && current->info != 43) { current = current->link; } if (current != nullptr) { temp->link = current->link; current->link = temp; } ```

Write Code to Print the Linked List

Traverse the list from the head, printing each node's `info` value. ```cpp current = head; while (current != nullptr) { std::cout << current->info << " "; current = current->link; } std::cout << std::endl; ```

Determine the Output of the Code

After completing all the insertions, the linked list will contain the elements in the following order: 43, 12, 72, 8. The print code will output: ``` 43 12 72 8 ```

Key concepts

Linked List Nodes

A linked list is a fundamental data structure used to organize data in a sequence. Unlike arrays, linked lists do not require contiguous memory allocation. Instead, they rely on nodes that are connected like a chain. Each node is an object which holds data and a reference to the next node in the sequence. In this exercise, we are dealing with a singly linked list. This means each node points to the next node only and there is no link to the previous node. This is a simple and effective way to manage data dynamically. Instead of being tied to a fixed size like arrays, linked lists can grow and shrink as needed.

Node Structure

The structure of a node is essential to understanding how linked lists work. In C++, a node is typically represented using a struct. The struct contains two main components: - **Data**: In this exercise, it's an integer value referred to as `info`. - **Link**: A pointer, named `link`, which points to the next node in the list. Here's a simple node structure: ```cpp struct Node { int info; Node *link; }; ``` This node structure allows each element of the list to not only store a value but also know where the next element is located in the memory. This dual configuration is what gives the linked list its structure and allows it to manage sequences effectively.

Linked List Insertion

Inserting elements into a linked list requires understanding of pointers and memory allocation. In our example, we are inserting elements in different scenarios: at the beginning, before a specific node, at the end, and after a specific node. - **At the start**: Insert `72` into an empty list by creating a new node and setting the head to this node. - **Before a node**: For `43`, a new node is created, its `link` points to what the head points to, then the head is adjusted to point to this new node. - **At the end**: For `8`, traverse the list until the last node is found, then change the last node's `link` to the new node. - **After a node**: For `12`, traverse until we find the node with `43`, adjust links such that `12` comes directly after it. Insertion processes vary depending on where you want to place the new data, but all involve creating a new node and adjusting links.

Print Linked List

To print a linked list, you traverse it from the head node, visiting each node until you reach the end of the list (which is marked by a `nullptr`). The key is to have a pointer that moves along the links of the list. The code to print a linked list usually follows this simple pattern: ```cpp Node *current = head; while (current != nullptr) { std::cout << current->info << " "; current = current->link; } std::cout << std::endl; ``` Each node's `info` is printed followed by a space. The loop continues until `current` reaches `nullptr`, indicating that we've reached the end of the list. This traversal method ensures that every value stored in the linked list is printed in the correct sequence.